ESQL Plugin Fails on SonarQube 25.x – Unknown Metrics (complexity_in_functions, complexity_in_procedures)

**Description**

We recently upgraded our SonarQube server to 25.4.0.105899 and the ESQL plugin stopped working during analysis.

**Environment**

- SonarQube Version: 25.4.0.105899 (Community Edition)
- ESQL Plugin Versions Tested:
- 3.4.0
- 3.5.0 (latest at the moment)
- 3.4.0-RC2 (previously working on SonarQube 9.9 LTS)
- Scanner Version: sonar-scanner-cli 7.3
- Java: 17
- Project Language: IBM ACE ESQL

**Issue**

After upgrading SonarQube, the scanner fails with:

```
java.lang.UnsupportedOperationException: Unknown metric: complexity_in_functions
```

or

```
Unknown metric: complexity_in_procedures
```

**Additional Details**

- These metrics were removed in SonarQube 10.x and above.
- The ESQL plugin still references legacy metrics that no longer exist in SonarQube 10+ / 25.x.
- Server startup logs show the plugin loading successfully, but the scan fails during Compute Engine analysis.

**Steps We Performed**

1. Upgraded SonarQube from 9.9 LTS → 25.4.
2. Updated scanner image to Java 17 (required by 25.x).
3. Reinstalled ESQL plugins (3.4.0, 3.5.0).
4. Restarted and validated plugin deployment.
5. Scan always fails during metric computation.

**Expected Behavior**

ESQL plugin should analyze ACE ESQL files without referencing removed metrics.

**Actual Behavior**

Scan fails before completion due to unsupported metrics.

**Error Log (Important Part)**

Caused by: java.lang.UnsupportedOperationException: Unknown metric: complexity_in_functions

(and similar for complexity_in_procedures)

**Impact**

- All ESQL-based ACE projects fail CI analysis.
- Quality Gate check cannot complete.
- No metrics appear in the SonarQube UI for ESQL files.

**Questions / Help Needed**

1. Is there an updated ESQL plugin compatible with SonarQube 25.x?
2. Are there plans to migrate this plugin to the new metric model?
3. Is there any workaround (e.g., disabling complexity metrics) to make the plugin work?

**Temporary Workaround**

We downgraded back to SonarQube 9.9 LTS, where esql-plugin-3.4.0-RC2.jar works fine.